The team soon assembled for an all-day ideation session at Taco Bell headquarters, where 30 different product concepts were considered, Purdue says, including new forms of burritos, nachos, and taquitos.

But one idea, from Doritos-maker Frito-Lay, stuck out: a Doritos-based taco shell pocketed with Taco Bell ingredients. "It was basically an image [of this taco] on a piece of paper, with a written description. I don't know what technology they use. We didn't even taste it; it was just more of, 'Hey, this is what it could look like,'" Purdue says. "It was like, 'Holy crap!' Nobody had ever done this before: turning a Dorito into a taco shell. It was just mind-blowing at the idea stage."

Steve Gomez, Taco Bell's food innovation expert, recalls seeing the first mock-up. "Every day I see a lot of concepts--sketches on paper, written words about products--and my job is to turn those products into reality," he says. "But in all my years as a product developer, I've never seen a concept like this. The product didn't even exist yet, and already people knew this idea was going to be huge."